Dipetalonema viteae microfilariae and adult worms from infected hamsters washed free of host components, are homogenized in Tris buffer and centrifuged to yield a supernatant (soluble somatic (SS) extract) and debris. The latter which is composed of cuticles and aqueous insoluble membranes is solubilized with Triton X (TX extract) or lithium diiodosalicylate (LDS extract). The SS, TX and LDS extracts of each parasitic stage are fractionated by gel filtrations on Sephadex G50, G100 and G200, by polyacrylamide gel electrophoresis and by isoelectrofocusing. Antisera to the various parasite extracts are raised in rabbits and the antigenic relationships between the parasitic stages and their extracts are examined by immunodiffusion and immunoelectrophoresis. In addition, antisera to various hamster (the parasite's host) tissue preparations are raised in rabbits and antigenic relationships between host and parasite can be examined. Attempts are being made to find successful in vitro culture conditions for the development of infection third to fourth stage larvae and for the maintenance of adult worms. Parasite metabolic antigens are derived from these cultures and are fractionated by the methods described above.